Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

Abstract

A polyester-based pressure-sensitive adhesive composition comprises a polyester obtained by condensation polymerization of at least a dicarboxylic acid having a side chain and a diol, a polyether polyol, and a crosslinking agent, wherein the polyester has a weight average molecular weight of 5000 to 50000, the polyether polyol contains a polyether polyol having hydroxyl groups at only part of terminals and/or all terminals, the polyether polyol having hydroxyl groups at only part of terminals has a number average molecular weight of 100 to 1500, and the polyether polyol having hydroxyl groups at only part of terminals is contained in an amount of 1 to 35 parts by weight based on 100 parts by weight of the polyester.

Claims

1. A polyester-based pressure-sensitive adhesive composition comprising a polyester, a polyether polyol, and a crosslinking agent, wherein the polyester is obtained by condensation polymerization of at least a dicarboxylic acid having a side chain and a diol, and the polyester does not contain a lactic acid unit, the polyester has a weight average molecular weight of 5000 to 50000, the polyether polyol contains a polyether polyol having hydroxyl groups at only part of the terminals and/or all terminals, the polyether polyol having hydroxyl groups at only part of the terminals has a number average molecular weight of 100 to 1500, and the polyether polyol having hydroxyl groups at only part of the terminals is contained in an amount of 1 to 35 parts by weight based on 100 parts by weight of the polyester.

2. The polyester-based pressure-sensitive adhesive composition according to claim 1, wherein the polyether polyol having hydroxyl groups at all terminals has a number average molecular weight of 100 to 5000, and the polyether polyol having hydroxyl groups at all terminals is contained in an amount of 1 to 400 parts by weight based on 100 parts by weight of the polyester.

3. The polyester-based pressure-sensitive adhesive composition according to claim 1, wherein the dicarboxylic acid and the diol are present in a mole ratio of 1:(1.08 to 2.10).

4. The polyester-based pressure-sensitive adhesive composition according to claim 1, wherein the side chain of the dicarboxylic acid is an alkyl group.

5. A pressure-sensitive adhesive sheet comprising a support and a pressure-sensitive adhesive layer obtained by crosslinking the polyester-based pressure-sensitive adhesive composition according to claim 1 and formed on at least one surface of the support.

6. The pressure-sensitive adhesive sheet according to claim 5, wherein the pressure-sensitive adhesive layer has a gel fraction of 40 to 95% by weight.

7. The pressure-sensitive adhesive sheet according to claim 5, which has an adhesive strength to glass of 1.0 N/25 mm or less.

8. The pressure-sensitive adhesive sheet according to claim 5, which is used for surface protection.

Description

EXAMPLES

(1) The present invention will be described more in detail with reference to Examples of the present invention; however, the present invention is not limited by Examples. In Examples, part(s) means part(s) by weight. The physical properties of polyesters and the blending contents and evaluation results of pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) are shown in Table 1 and Table 2.

(2) <Preparation of Polyester A-1>

(3) A three-neck separable flask equipped with a stirrer, a thermometer and a condenser was charged with 100.9 parts of a dimer acid (trade name: Pripol 1009, manufactured by Croda, weight average molecular weight: 567) as a dicarboxylic acid and 100 parts of a dimer diol (trade name: Pripol 2033, manufactured by Croda, weight average molecular weight: 537) as a diol so that the mole ratio of the dimer acid and the dimer diol was 1:1.05, and 0.1 parts of titanium tetraisopropoxide (manufactured by Kishida Chemical Co., Ltd.) as a catalyst, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPA). The reaction was continued for about 5 hours to obtain a polyester A-1. The polyester A-1 had a weight average molecular weight (Mw) of 55000.

(4) <Preparation of Polyester A-2>

(5) A three-neck separable flask equipped with a stirrer, a thermometer and a condenser was charged with 92.2 parts of a dimer acid (trade name: Pripol 1009, manufactured by Croda, weight average molecular weight: 567) as a dicarboxylic acid and 100 parts of a dimer diol (trade name: Pripol 2033, manufactured by Croda, weight average molecular weight: 537) as a diol so that the mole ratio of the dimer acid and the dimer diol was 1.00:1.15, and 0.1 parts of titanium tetraisopropoxide (manufactured by Kishida Chemical Co., Ltd.) as a catalyst, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPA). The reaction was continued for about 5 hours to obtain a polyester A-2. The polyester A-2 had a weight average molecular weight (Mw) of 23000.

(6) <Preparation of polyester A-3>

(7) A three-neck separable flask equipped with a stirrer, a thermometer and a condenser was charged with 70.7 parts of a dimer acid (trade name: Pripol 1009, manufactured by Croda, weight average molecular weight: 567) as a dicarboxylic acid and 100 parts of a dimer diol (trade name: Pripol 2033, manufactured by Croda, weight average molecular weight: 537) as a diol so that the mole ratio of the dimer acid and the dimer diol was 1.00:1.50, and 0.1 parts of titanium tetraisopropoxide (manufactured by Kishida Chemical Co., Ltd.) as a catalyst, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPA). The reaction was continued for about 5 hours to obtain a polyester A-3. The polyester A-3 had a weight average molecular weight (Mw) of 9000.

(8) <Preparation of Polyester A-4>

(9) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 619 parts of a dimer acid (trade name: Pripol 1009, manufactured by Croda, weight average molecular weight: 567) as a dicarboxylic acid and 100 parts of propylene glycol (trade name: Propylene glycol, manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight: 76) as a diol so that the mole ratio of the dimer acid and the propylene glycol was 1.00:1.20, and 0.1 parts of dibutyltin(IV) oxide (manufactured by Kishida Chemical Co., Ltd.) as a catalyst, and the contents were heated to 160 C. and kept at this temperature while being stirred in normal pressure. While water produced by the reaction was removed by the condenser, the reaction was continued for about 14 hours. Further, the nitrogen introduction tube and the condenser having a trap were taken out and a vacuum pump was attached, and then the contents were kept at 160 C. while being stirred in a reduced pressure atmosphere (0.002 MPA). The reaction was continued for about 4 hours to obtain a polyester A-4. The polyester A-4 had a weight average molecular weight (Mw) of 4000.

(10) <Preparation of Polyester A-5>

(11) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 502 parts of a dimer acid (trade name: Pripol 1009, manufactured by Croda, weight average molecular weight: 567) as a dicarboxylic acid and 100 parts of 1,4-butanediol (trade name: 1,4-Butanediol, manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight: 90) as a diol so that the mole ratio of the dimer acid and the 1,4-butanediol was 1.00:1.25, and 0.1 parts of dibutyltin(IV) oxide (manufactured by Kishida Chemical Co., Ltd.) as a catalyst, and the contents were heated to 200 C. and kept at this temperature while being stirred in normal pressure. While water produced by the reaction was removed by the condenser, the reaction was continued for about 4 hours. Further, the nitrogen introduction tube and the condenser having a trap were taken out and a vacuum pump was attached, and then the contents were kept at 200 C. while being stirred in a reduced pressure atmosphere (0.010 MPA). The reaction was continued for about 4 hours to obtain a polyester A-5. The polyester A-5 had a weight average molecular weight (Mw) of 24000.

(12) <Preparation of Polyester A-6>

(13) A three-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts by weight of a dimer acid (trade name: Pripol 1009, manufactured by Croda, molecular weight: 567) as a dicarboxylic acid and 24 parts by weight of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol so that the mole ratio of the dimer acid and the 1,4-butanediol was 1:1.56, and 0.2 parts by weight of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in nitrogen atmosphere.

(14) Thereafter, the nitrogen introduction tube and the condenser were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 10 hours to obtain a polyester A-6. The polyester A-6 had a weight average molecular weight (Mw) of 10000.

(15) <Preparation of Polyester A-7>

(16) A three-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts by weight of a dimer acid (trade name: Pripol 1009, manufactured by Croda, molecular weight: 567) as a dicarboxylic acid and 17.5 parts by weight of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol so that the mole ratio of the dimer acid and the 1,4-butanediol was 1:1.1, and 0.2 parts by weight of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in nitrogen atmosphere.

(17) Thereafter, the nitrogen introduction tube and the condenser were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 4 hours to obtain a polyester A-7. The polyester A-7 had a weight average molecular weight (Mw) of 70000.

(18) <Polyether Polyol>

(19) B-1: Trade name: Sannix PP-400, manufactured by Sanyo Chemical Industries, Ltd., polypropylene glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 400

(20) B-2: Trade name: Sannix PP-2000, manufactured by Sanyo Chemical Industries, Ltd., polypropylene glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 2000

(21) B-3: Trade name: Smack MP-70, manufactured by Kao Corporation, polypropylene glycol containing methyl ether group at one terminal, number average molecular weight (Mn): 439

(22) B-4: Trade name: Reokon 1015H, manufactured by Lion Corporation, polypropylene glycol containing 2-ethylhexyl ether group at one terminal, number average molecular weight (Mn): 800

(23) B-5: Trade name: BLAUNONBUP-1900, manufactured by Aoki Oil Industrial Co., Ltd., polypropylene glycol containing butyl ether group at one terminal, number average molecular weight (Mn): 1900

(24) B-6: Trade name: Uniol PB-500, manufactured by NOF Corporation, polybutylene glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 500

(25) B-7: Trade name: PEG-400, manufactured by Sanyo Chemical Industries, Ltd., polyethylene glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 400

(26) B-8: Trade name: PTG-1000SN, manufactured by Hodogaya Chemical Co., Ltd., polytetramethylene ether glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 1000

(27) B-9: Trade name: PTG-3000SN, manufactured by Hodogaya

(28) Chemical Co., Ltd., polytetramethylene ether glycol, number average molecular weight (Mn): 3000

(29) B-10: Trade name: PTG-2000SN, manufactured by Hodogaya Chemical Co., Ltd., polytetramethylene ether glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 2000

(30) B-11: Trade name: Cerenol H1000, manufactured by DuPont, polytrimethylene ether glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 1000

(31) B-12: Trade name: Sannix PP-3000, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glycol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 3200

(32) B-13: Trade name: PTG-L1000, manufactured by Hodogaya Chemical Co., Ltd., copolyether polyol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 1000

(33) B-14: Trade name: PTG-L2000, manufactured by Hodogaya Chemical Co., Ltd., copolyether polyol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 2000

(34) B-15: Trade name: PTG-L3000, manufactured by Hodogaya Chemical Co., Ltd., copolyether polyol containing hydroxyl groups at both terminals, number average molecular weight (Mn): 3000

(35) <Crosslinking Agent>

(36) C-1: Trade name: Desmodur N3600, manufactured by Sumika Bayer Co., Ltd., isocyanurate-based polyhexamethylene diisocyanate

(37) C-2: Trade name: CORONATE HK, manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanurate polymeric form polyhexamethylene diisocyanate

(38) C-3: Trade name: DURANATE D101, manufactured by Asahi Kasei Chemicals Corporation, hexamethylene diisocyanate

(39) C-4: Trade name: TPA-100, manufactured by Asahi Kasei Chemicals Corporation, polyhexamethylene diisocyanate

Example 1

(40) Twenty-five parts of the polyether polyol B-3, and, as a crosslinking agent, 25 parts of isocyanurate-based polyhexamethylene diisocyanate (trade name: Desmodur N3600, manufactured by Sumika Bayer Co., Ltd.) and 50 to 150 parts of toluene as a solvent were blended with 100 parts of the polyester A-3 to adjust viscosity (e.g., about 10 Pa.Math.s) for easy application and processing, so that a polyester-based pressure-sensitive adhesive composition was obtained. This composition was applied to a polyethylene terephthalate (PET) film (trade name: Lumirror 38 S10, manufactured by PANAC Corporation) with 38 m thickness as a substrate in such a manner that the pressure-sensitive adhesive layer obtained by drying (after drying) had a thickness of 10 m, and dried at 100 C. for 3 minutes to obtain a pressure-sensitive adhesive layer. Thereafter, the pressure-sensitive adhesive layer was bonded to the peeling-treated surface of a polyethylene terephthalate (PET) film (thickness: 38 m, trade name: Diafoil MRE#38, manufactured by Mitsubishi Plastics Inc.) subjected to peeling treatment, and the resultant was left at 40 C. for 7 days to obtain a pressure-sensitive adhesive sheet (for surface protection) having a support and a pressure-sensitive adhesive layer formed on the support.

Examples 2 to 8 and Comparative Examples 1 to 5

(41) Pressure-sensitive adhesive sheets were obtained in the same manner as in Example 1, except that compositions were prepared by mixing the contents as shown in Table 1.

Example 9

(42) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 1, except that 50 parts of polyhexamethylene diisocyanate (trade name: TPA-100, manufactured by Asahi Kasei Chemicals Corporation) as a crosslinking agent and 30 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 1000 (trade name: PTG-1000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 10

(43) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 100 parts of the crosslinking agent and 300 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 1000 (trade name: PTG-1000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 11

(44) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 30 parts of the crosslinking agent and 30 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 3000 (trade name: PTG-3000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 12

(45) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 60 parts of the crosslinking agent and 300 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 3000 (trade name: PTG-3000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 13

(46) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 60 parts of the crosslinking agent and 150 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 2000 (trade name: PTG-2000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 14

(47) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 70 parts of the crosslinking agent and 150 parts of polytrimethylene ether glycol having a number average molecular weight (Mn) of 1000 (trade name: Cerenol H1000, manufactured by DuPont) were blended with 100 parts of the polyester A-6.

Example 15

(48) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 40 parts of the crosslinking agent and 150 parts of polyoxypropylene glycol having a number average molecular weight (Mn) of 3200 (trade name: Sannix PP-3000, manufactured by Sanyo Chemical Industries Ltd.) were blended with 100 parts of the polyester A-6.

Example 16

(49) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 70 parts of the crosslinking agent and 150 parts of copolyether polyol having a number average molecular weight (Mn) of 1000 (trade name: PTG-L1000, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 17

(50) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 60 parts of the crosslinking agent and 150 parts of copolyether polyol having a number average molecular weight (Mn) of 2000 (trade name: PTG-L2000, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Example 18

(51) A pressure-sensitive adhesive sheet (for surface protection) was obtained in the same manner as in Example 9, except that 40 parts of the crosslinking agent and 150 parts of copolyether polyol having a number average molecular weight (Mn) of 3000 (trade name: PTG-L3000, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-6.

Comparative Example 6

(52) A pressure-sensitive adhesive sheet (applicable for surface protection) was obtained in the same manner as in Example 9, except that 20 parts of the crosslinking agent and 150 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 3000 (trade name: PTG-3000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A-7.

(53) (Weight Average Molecular Weight)

(54) The weight average molecular weight (Mw) was measured as follows: about 0.2 g of each polyester was collected on a petri dish, and the solvent was removed by drying at 120 C. for 2 hours. Then, 0.01 g of the polyester layer on the petri dish was weighed, which was added to 10 g of tetrahydrofuran (THF) and left for 24 hours for dissolution. The obtained solution was subjected to gel permeation chromatography (GPC), and the molecular weight of each polyester was measured based on the calibration curve produced using standard polystyrene.

(55) (Measurement Conditions)

(56) Apparatus name: HLC-8220GPC, manufactured by Tosoh

(57) Corporation

(58) Test piece concentration: 0.1% by weight (THF solution)

(59) Test piece injection amount: 20 l

(60) Fluent: THF

(61) Flow rate: 0.300 ml/min

(62) Measurement (column) temperature: 40 C.

(63) Column: Test piece column; TSKguardcolumn SuperHZ-L (1 column)+TSKgel SuperHZM-M (2 columns), reference column; TSKgel SuperH-RC (1 column), manufactured by Tosoh Corporation

(64) Detector: Differential refractometer (RI)

(65) (Number Average Molecular Weight)

(66) The number average molecular weight (Mn) was also measured in the same manner as in the weight average molecular weight (Mw).

(67) (Gel Fraction of Pressure-Sensitive Adhesive Layer)

(68) Each of the pressure-sensitive adhesive sheets having a thickness of 30 m obtained in Examples and Comparative Examples was cut in a size of 5 cm5 cm. The support was removed from the cut pressure-sensitive adhesive sheet to obtain a test piece, and this test piece was wrapped with a Teflon (registered trade name) sheet with a known weight, and the obtained test piece was weighed and then left at 23 C. for 7 days in toluene to extract the sol component from the test piece. Thereafter, the resulting test piece was dried at 120 C. for 2 hours and then weighed. The gel fraction was calculated according to the following equation.
Gel fraction (% by weight)=(weight after dryingweight of Teflon(registered trade name)sheet)/(weight before dryingweight of Teflon(registered trade name)sheet)100
(Adhesive Strength: Initial Period)

(69) Each of the pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer with a thickness of 10 m obtained in Examples and Comparative Examples was cut in 25 mm width, and the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet was bonded to a tin-untreated surface of alkali glass (manufactured by Matsunami Glass Ind., Ltd.) to obtain each test piece, and the adhesive strength to the alkali glass (N/25 mm) was measured. The pressure bonding at the time of bonding was carried out by reciprocating a 2 kg roller one time, and the measurement of adhering strength (adhesive strength) at 180 peeling was carried out using a tensile compression tester (apparatus name: TG-1 kN, manufactured by Minebea Co., Ltd.) in the following conditions.

(70) Tension (peeling) rate: 300 mm/min

(71) Measurement conditions: temperature: 232 C., humidity 655% RH

(72) (Adhesive Strength: Over Time)

(73) Each test piece prepared in the same manner as in the initial period evaluation was preserved in an atmosphere of a temperature of 60 C. and a humidity of 90% for 3 days, and thereafter left still at room temperature for 1 hour or more, and then, the adhering strength measurement was carried out in the same manner as in the initial period evaluation.

(74) The adhesive strength (initial period) and the adhesive strength (over time) are both preferably 1.0 N/25 mm or less, more preferably 0.9 N/25 mm or less, and particularly preferably 0.8 N/25 mm or less. If the adhesive strength exceeds 1.0 N/25 mm, the adhesive strength is too high so that light peelability (removability) cannot be attained, and for example, in the case of using the test piece as a pressure-sensitive adhesive sheet for surface protection, adhesive residues may remain on an adherend at the time of peeling thereafter, and the support (substrate) may be damaged, and therefore it is not preferable.

(75) (Anti-Staining Property)

(76) Presence or absence of staining on an adherend was evaluated in accordance with presence or absence of traces of bleeding out or presence or absence of adhesive residues by observing, with naked eyes, the surface of the adherend which had contact with pressure-sensitive adhesive layer after the measurement of the adhesive strength.

(77) (Wettability)

(78) Each of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was cut in 25 mm width and 70 mm length, and the pressure-sensitive adhesive surface was dropped calmly onto a glass plate, and the motion-pictures of widening of the surface area of the pressure-sensitive adhesive surface per one second were taken by a video camera. The color shades owing to wetting were then binarized for every 0.5 seconds so that the wet surface area was measured, and the wetting rate (cm.sup.2/s) was calculated for evaluation. Presence or absence of inclusion of air bubbles was also observed together with the evaluation of wettability.

(79) The wetting rate of the pressure-sensitive adhesive sheet of the present invention is preferably 1.8 cm.sup.2/s or more, more preferably 2.0 cm.sup.2/s or more, and particularly preferably 3.0 cm.sup.2/s. If the wetting rate is less than 1.8 cm.sup.2/s, handleability may be inferior and air bubbles may be easily included, and the appearance of the adherend to which a surface protective sheet is bonded is worsened, and therefore it is not preferable.

(80) TABLE-US-00001 TABLE 1 Blending contents and Example evaluation results 1 2 3 4 5 6 7 Polyester A-1 Mw: 55000 A-2 Mw: 23000 100 100 100 A-3 Mw: 9000 100 100 A-4 Mw: 4000 A-5 Mw: 24000 100 100 Polyether B-1 Mn: 400 25 polyol B-2 Mn: 2000 30 B-3 Mn: 439 25 15 B-4 Mn: 800 25 B-5 Mn: 1900 B-6 Mn: 500 25 B-7 Mn: 400 25 Crosslinking C-1 20 15 20 20 25 20 agent C-2 15 C-3 5 Gel fraction % by 69 61 75 64 81 70 94 weight Adhesive Initial N/25 mm 0.05 0.12 0.17 0.04 0.60 0.06 0.07 strength period Adhesive Over N/25 mm 0.06 0.28 0.21 0.20 0.30 0.35 0.12 strength time Presence or absence Absence Absence Absence Absence Absence Absence Absence of staining Wetting rate cm.sup.2/sec 6.2 5.2 4.8 8.2 5.2 5.8 7.2 Determination (applicable for surface protection) Blending contents and Example Comparative Example evaluation results 8 1 2 3 4 5 Polyester A-1 Mw: 55000 100 A-2 Mw: 23000 100 100 A-3 Mw: 9000 100 A-4 Mw: 4000 100 A-5 Mw: 24000 100 Polyether B-1 Mn: 400 6 polyol B-2 Mn: 2000 B-3 Mn: 439 40 25 20 B-4 Mn: 800 B-5 Mn: 1900 25 B-6 Mn: 500 B-7 Mn: 400 Crosslinking C-1 10 20 20 15 30 agent C-2 9 C-3 6 Gel fraction % by 91 90 23 78 62 97 weight Adhesive Initial N/25 mm 0.16 1.20 0.03 0.001 2.40 0.02 strength period Adhesive Over N/25 mm 0.75 3.50 0.02 0.005 4.50 0.03 strength time Presence or absence Absence Absence Presence Presence Absence Absence of staining Wetting rate cm.sup.2/sec 6.8 5.1 9.6 10.2 5.8 1.6 Determination (applicable x x x x x for surface protection)

(81) TABLE-US-00002 TABLE 2 Blending contents and Example evaluation results 9 10 11 12 13 14 15 Polyester A-6 Mw: 10000 100 100 100 100 100 100 100 A-7 Mw: 70000 Polyether B-8 Mn: 1000 30 300 polyol B-9 Mn: 3000 30 300 B-10 Mn: 2000 150 B-11 Mn: 1000 150 B-12 Mn: 3200 150 B-13 Mn: 1000 B-14 Mn: 2000 B-15 Mn: 3000 Crosslinking C-4 50 100 30 60 60 70 40 agent Gel fraction % by 95 98 97 98 96 98 97 weight Adhesive Initial N/25 mm 0.10 0.10 0.10 0.10 0.10 0.10 0.10 strength period Presence or absence Absence Absence Absence Absence Absence Absence Absence of staining Wetting rate cm.sup.2/sec 7.6 8.2 8.1 8.5 7.9 7.8 7.6 Inclusion of air Absence Absence Absence Absence Absence Absence Absence bubbles Comparative Blending contents and Example Example evaluation results 16 17 18 6 Polyester A-6 Mw: 10000 100 100 100 A-7 Mw: 70000 100 Polyether B-8 Mn: 1000 polyol B-9 Mn: 3000 150 B-10 Mn: 2000 B-11 Mn: 1000 B-12 Mn: 3200 B-13 Mn: 1000 150 B-14 Mn: 2000 150 B-15 Mn: 3000 150 Crosslinking C-4 70 60 40 20 agent Gel fraction % by 97 98 98 80 weight Adhesive Initial N/25 mm 0.10 0.10 0.10 1.50 strength period Presence or absence Absence Absence Absence Absence of staining Wetting rate cm.sup.2/sec 8 8.2 8.3 2.5 Inclusion of air Absence Absence Absence Presence bubbles

(82) From the results of evaluation in Table 1, regarding Examples 1 to 8, since desirable polyesters and polyether polyols were used, pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) were obtained which had desired gel fraction and adhesive strength (peel strength), had good wettability at the time of bonding to an adherend and excellent workability, had no adhesive residues even after being peeled off, and had excellent light peelability (removability), preventing properties for increasing adhesive strength, anti-staining properties and workability. It was confirmed that in the pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets), a wide range of pressure-sensitive adhesion design is possible. Particularly, it was confirmed that a pressure-sensitive adhesive sheet suitable for surface protection could be obtained. In Examples 9 to 18, it was also confirmed that inclusion of air bubbles did not occur. In Examples 10 to 18, specified polyether polyols were used, and therefore inclusion of air bubbles was not observed and the pressure-sensitive adhesive layers were useful.

(83) On the other hand, in Comparative Example 1, because a polyether polyol was not used, not only the adhesive strength in initial period but also the adhesive strength over time were high, and it was confirmed that light peelability (removability) and preventing properties for increasing adhesive strength were inferior. In Comparative Example 2, the blending amount of the polyether polyol was large, gelation did not proceed as expected, the gel fraction of the pressure-sensitive adhesive layer was significantly low, and staining was observed. Further, in Comparative Example 3, the weight average molecular weight of the polyester polyol was high and staining was observed. In Comparative Example 4, because the polyether polyol having a weight average molecular weight exceeding the desired range was used, not only the adhesive strength in initial period but also the adhesive strength over time was high, and it was confirmed that light peelability (removability) and preventing properties for increasing adhesive strength were inferior. In Comparative Example 5, because the polyester having a weight average molecular weight less than the desired range was used, it was confirmed that the gel fraction was increased, the wetting rate was very slow, and workability was inferior. In Comparative Example 6, because the polyester having a weight average molecular weight exceeding the desirable range was used, the adhesive strength in initial period was too high and inclusion of air bubbles was also confirmed.